Commitments and Contingencies - Future Minimum Payments Under Non-Cancelable Leases, Sublease Commitments and Related Payments (Details) $ in Millions	Dec. 31, 2017 USD ($)
Payments [Abstract]
2018	$ 131.6
2019	127.8
2020	107.5
2021	102.3
2022	91.3
2023 and thereafter	204.2
Total future minimum payments	764.7
Sublease Receipts [Abstract]
2018	44.2
2019	46.0
2020	29.7
2021	28.4
2022	25.3
2023 and thereafter	48.9
Total future minimum payments receivable	222.5
Net Payments [Abstract]
2018	87.4
2019	81.8
2020	77.8
2021	73.9
2022	66.0
2023 and thereafter	155.3
Total future net minimum payments	$ 542.2